U.S. Sen. Mark Pryor of Arkansas says expected Republican rival Tom Cotton has "alienated" farmers, students and many others in the state with his votes since being sworn in to Congress in January.

Pryor told The Associated Press on Friday that he's preparing for a tough race against Cotton, who is expected to announce his bid to challenge Pryor next week. Cotton was elected to south Arkansas' 4th Congressional District last November.

Pryor criticized Cotton's vote against an initial version of the farm bill, a student loan measure and the Violence Against Women Act. He said he believed Arkansans would judge Cotton based on those votes.

Pryor, who is seeking a third term, is viewed by Republicans as the most vulnerable Senate incumbent on the ballot next year.